1. Field of the Invention
The present invention relates to vascular tissue, or more particularly, to a system and method of using backscattered data and known parameters to characterize vascular tissue.
2. Description of Related Art
The present invention relates to the intra-vascular ultrasound (IVUS) analysis arts. It finds particular application to a system and method for quantitative component identification within a vascular object including characterization of tissue. It should be appreciated that while the present invention is described in terms of an ultrasonic device, or more particularly the use of IVUS data (or a transformation thereof) to characterize a vascular object, the present invention is not so limited. Thus, for example, using backscattered data (or a transformation thereof) to characterize any tissue type or composition is within the spirit and scope of the present invention.
Ultrasonic imaging of portions of a patient's body provides a useful tool in various areas of medical practice for determining the best type and course of treatment. Imaging of the coronary vessels of a patient by ultrasonic techniques can provide physicians with valuable information. For example, the image data may show the extent of a stenosis in a patient, reveal progression of disease, help determine whether procedures such as angioplasty or atherectomy are indicated or whether more invasive procedures may be warranted.
In a typical ultrasound imaging system, an ultrasonic transducer is attached to the end of a catheter that is carefully maneuvered through a patient's body to a point of interest such as within a blood vessel. The transducer may be a single-element crystal or probe that is mechanically scanned or rotated back and forth to cover a sector over a selected angular range. Acoustic signals are then transmitted and echoes (or backscatter) from these acoustic signals are received. The backscatter data can be used to identify the type or density of a scanned tissue. As the probe is swept through the sector, many acoustic lines are processed building up a sector-shaped image of the patient. After the data is collected, an image of the blood vessel (i.e., an IVUS image) is reconstructed using well-known techniques. This image is then visually analyzed by a cardiologist to assess the vessel components and plaque content.
Typically, the ultrasonic image data is transferred to a VHS videotape, digitized and then analyzed. This process, however, loses image resolution since the videotape typically has a lower resolution than the originally collected backscatter data. Losing image resolution may result in an inaccurate evaluation of a vessel and its plaque content. Furthermore, certain image characteristics like brightness and contrast will be different for different patients or could vary for the same patient if the cardiologist varies the settings on the IVUS console. The images that are recorded on the videotapes are the same images viewed on the IVUS console screen and, thus, subject to the settings on the console. Since plaque (or tissue type) is identified by its appearance on the screen, errors may occur in the analysis if the screen settings have been modified. Another drawback is that certain information (e.g., tissue composition, etc.) cannot readily be discerned from an IVUS image (at least not to any degree of certainty). Thus, it would be advantageous to have a system and method of characterizing and/or imaging a vascular object that overcomes at least one of these drawbacks.